1. Technical Field
Illustrative embodiments described in this patent specification generally relate to a cleaning device included in an image forming apparatus employing an electrophotographic method, a process cartridge, and the image forming apparatus.
2. Description of the Related Art
Related-art image forming apparatuses, such as copiers, printers, facsimile machines, or multifunction devices having two or more of copying, printing, and facsimile functions, typically form a toner image on a recording medium (e.g., a sheet of paper, etc.) according to image data using an electrophotographic method. In such a method, for example, a charger charges a surface of an image carrier (e.g., a photoconductor); an irradiating device emits a light beam onto the charged surface of the photoconductor to form an electrostatic latent image on the photoconductor according to the image data; a developing device develops the electrostatic latent image with a developer (e.g., toner) to form a toner image on the photoconductor; a transfer device transfers the toner image formed on the photoconductor onto a sheet; and a fixing device applies heat and pressure to the sheet bearing the toner image to fix the toner image onto the sheet. The sheet bearing the fixed toner image is then discharged from the image forming apparatus.
The photoconductor rotatable to carry the toner image thereon is generally provided with a cleaning device to clean the surface of the photoconductor. The cleaning device includes, for example, a first blade contacting the surface of the photoconductor and a second blade contacting the surface of the photoconductor at a position downstream from the first blade relative to a direction of rotation of the photoconductor with respect to, as a reference point, a primary transfer position on the surface of the photoconductor. The primary transfer position is where the toner image formed on the surface of the photoconductor is transferred onto a transfer body of the transfer device.
The first and second blades are often provided such that a leading end thereof is positioned upstream from a trailing end thereof relative to the direction of rotation of the photoconductor to efficiently remove residual toner and lubricant adhering to the surface of the photoconductor. In other words, the blades are often provided to contact the surface of the photoconductor against the direction of rotation of the photoconductor.
Regarding the second blade, for example, in addition to the leading end thereof facing up, a first edge of the leading end is caused to contact the surface of the photoconductor at a position higher than a second edge of the leading end of the second blade. By contrast, a second blade in which a leading end thereof is caused to face down is disclosed in Published Unexamined Japanese Patent Application No. 2005-352310 (hereinafter referred to as JP-2005-352310-A).
In another approach, Published Unexamined Japanese Patent Application No. 2000-330443 (hereinafter referred to as JP-2000-330443-A) discloses a cleaning device including a first blade and a second blade in which a leading end of the second blade is caused to face up, and a first edge of the leading end of the second blade is caused to contact a surface of a photoconductor at a position lower than a second edge of the leading end thereof. A lubricant such as zinc stearate fills a space formed by the surface of the photoconductor and the first and second blades, and the second blade is used exclusively to level the lubricant supplied to the surface of the photoconductor.
The residual toner and the lubricant adhering to the surface of the photoconductor can be efficiently removed by the above-described blades contacting the surface of the photoconductor against the direction of rotation of the photoconductor. However, an extreme decrease in the amount of the residual toner and the lubricant entering the space between the surface of the photoconductor and the edges of the blades contacting the surface of the photoconductor can cause problems such as chipping and curling of the blades, noise, and abnormal friction.
Because the residual toner adhering to the surface of the photoconductor immediately after transfer of the toner image onto the transfer member constantly enters the space between the surface of the photoconductor and the edge of the first blade, the above-described problems do not occur at the first blade. By contrast, however, the above-described problems may occur at the second blade because most of the residual toner adhering to the surface of the photoconductor is scraped off by the first blade.
In the first two examples of the second blades described above, because the first edge of the leading end thereof contacting the surface of the photoconductor is positioned above the second edge of the leading end thereof, or the leading end thereof faces down, the residual toner and the lubricant constantly fall from the edge of the second blade, possibly increasing occurrences of the above-described problems.
In a case in which the first blade, the lubricant or a lubricant applicator, and the second blade are provided, in that order, downstream from the primary transfer position on the surface of the photoconductor (that is, downstream relative to the direction of rotation of the photoconductor), the second blade is used to level the lubricant applied to the surface of the photoconductor. However, in the cleaning devices of the related art, because the second blade levels the lubricant supplied to the surface of the photoconductor in the same direction as a direction of fall of the lubricant scraped off thereby, when the lubricant is not evenly supplied to the surface of the photoconductor to begin with the second blade may not function to reliably level the lubricant on the surface of the photoconductor.
As described above, with the second blade disclosed in JP-2000-330443-A, the first edge of the leading end thereof is caused to contact the surface of the photoconductor at a position lower than the second edge of the leading end thereof. In addition, the lubricant is provided within a space defined by the first and second blades and the surface of the photoconductor. Consequently, although the two blades are provided as described above, actually, only the first blade serves as a blade for scraping off the residual toner adhering to the surface of the photoconductor. In other words, the residual toner adhering to the surface of the photoconductor is not effectively scraped off at two positions. An additional problem is that, because it closely contacts the lubricant, the second blade might not be sufficiently elastically deformed, possibly causing uneven leveling of the lubricant on the surface of the photoconductor as a result.